The prior art discloses numerous machines including a pair of elongated forming racks for rolling splines or teeth in a round workpiece. With this type of machine, driven movement of the pair of racks in opposite directions from each other engages forming teeth of the racks with the round workpiece at diametrically opposite locations to form splines in the workpiece. The splining is conventionally completed during a single stroking action of the dies such that the length of the splines formed is equal to the width of rack tooth engagement with the workpiece, which is normally equal to the width of the forming racks. Usually the complete splining operation is performed by a single stroking action of the racks from a first end-to-end position through an overlapping relationship and to a second end-to-end position. Unloading can be performed in the second end-to-end position or after reverse movement of the racks back to the first end-to-end position. Furthermore, it is also possible to perform splining of long splines having a greater length than the width of the racks by two or more strokes with axially indexing of the workpiece between the strokes.
Spline rolling as described above cannot be performed when a coarse pitch is involved, i.e. less than 16 splines per inch along the pitch circle, since the amount of material movement produces too great a load on the rack teeth. As such, coarse pitch splines have previously been formed by a suitable metal removal operation such as broaching or hobbing, etc. However, such metal removal operations are much more time consuming and expensive than spline rolling.
U.S. Pat. No. 3,043,169 discloses apparatus for pressure forming teeth or splines on a workpiece by a pair of elongated tools having round cross sections with teeth spaced along their lengths. Opposite ends of each tool are supported by associated holders on slidable bases and are driven in a spaced relationship to each other in a reciprocal manner as a rotatable workpiece is moved along its axis of rotation between the tools. Wedges on each slidable base engage the associated tool intermediate its ends with line contacts during the splining. After the splining, the round tools are rocked away from the wedges to permit unloading of a splined workpiece. Also, each of the slidable bases is driven by an extendable and retractable hydraulic cylinder which can tend to buckle in the extending mode of movement such that the splining is not performed as accurately as may be desired.